Closure apparatuses of that kind are disclosed for example in the journals RADEX-Rundschau, 1980, issue 3, pages 187 to 196, and Stahl und Eisen 104 (1984), No 1, pages 27 to 30. In those constructions, the shut-off member is in the form of a pivotable flap which in the closed position bears against the tap hole from below and prevents granular refractory material introduced into the tap hole before the furnace is charged from flowing out. During the smelting operation, the filling material prevents direct contact between the shut-off member and the molten bath. For the purposes of tapping the vessel, the flap is pivoted to the side, the filling material drops out and the molten material flows out of the hearth into a tapping truck. If, by virtue of the filling material coming into contact with the molten bath, sintered bridges which prevent the foregoing procedure from being carried out have been formed in the filling material, the tapping operation is started by a brief burn with oxygen. After the molten bath has run out, the closure flap is closed again and the tapping passage is filled with granular refractory material before the next furnace charge is introduced.
If, when tapping off a metallurgical vessel with a closure apparatus of the above-indicated kind, a residual portion of the molten metal and the slag is retained in the vessel in order to improve the smelting or metallurgical process in respect of the next charge (that mode of operation is referred to as the sump process), then it is necessary for the vessel to be designed in such a way that it can be tilted in order to ensure that the closure system is not subjected to wear by the fluid metal or slag. Expensive arrangements are required for that purpose, in vessels of larger sizes.
Austrian patent specification No. 207 053 discloses a bottom closure arrangement for casting ladles and the like, wherein the bottom opening in the vessel can be closed by a plug bar, wherein the tap hole is arranged to be heated, and wherein in addition there is a shut-off member in the form of a pivotable flap or a pivotable plug which is adapted to close the tap hole from below. The plug bar which can be drawn entirely out of the molten bath makes it possible for the pouring jet of liquid material to be regulated or stopped during the operation of pouring out the molten bath. Desirably, the last part of the molten bath is held back by means of the lower shut-off member, and caused to harden in order to form a new sealed plug for the next charge. As soon as that plug has been formed, the lower plate can be pivoted to one side again so that it is not subjected to any thermal or mechanical loading during the smelting process. Heating of the tap hole causes the hardened plug to be liquefied and the pouring operation started. Although that closure apparatus makes it possible to perform the above-mentioned sump process without tilting the vessel, the lower closure member is in this case subjected to the effect of the liquid metal, and in addition a heating means must be provided in the region of the tap hole.
In a closure apparatus of the kind set forth above, wherein the shut-off member which closes off the tap hole from below is protected from direct contact with the molten metal bath, an object of the present invention is to make it possible, without tilting the vessel, to carry out a `sump process` wherein a residual portion of the molten metal bath and the slag floating on the metal bath are held back in the vessel. The invention further seeks to provide that, by means of the closure apparatus, oxygen can be supplied for opening the tap hole when starting the tapping operation and a filling material for filling the tap hole can be supplied after the tapping operation has been concluded. The invention further seeks to provide that the parts of the closure apparatuses, which are subjected to a thermal loading, can be simply cooled.